For example, Patent Document 1 discloses an electronic component in which a semiconductor element is accommodated in a high-frequency package. FIG. 1 is an exploded perspective view of an electronic component 11 disclosed in Patent Document 1, and FIG. 2 is a sectional view of the electronic component 11 of Patent Document 1. In the electronic component 11, a portion above a semiconductor element 13 mounted on an upper surface of a board 12 is covered with a metallic cap 14. The semiconductor element 13 mounted on the upper surface of the board 12 is connected to a pad 16 through a bonding wire 15, and the pad 16 is connected to a lead electrode 18 in a rear surface through a via hole 22. A ring-like ground electrode 19 is provided in an outer peripheral portion in the upper surface of the board 12 so as to surround the circuit region, and the ground electrode 19 is connected to a ground pattern 20 in the rear surface of the board 12 through a via hole 17. The metallic cap 14 is bonded to the ground electrode 19 by a conductive resin bonding agent 21, and the metallic cap 14 is electrically connected to the ground electrode 19 while mechanically fixed to the ground electrode 19. The ground electrode 19 to which the metallic cap 14 is connected is provided in the upper surface of the board 12, thereby preventing a harmful influence of an electronic capacitance C between the lead electrode 18 and the metallic cap 14 on a circuit function.
However, in the electronic component 11 having the structure of Patent Document 1, the conductive resin bonding agent 21 flows out to the inside, and occasionally the conductive resin bonding agent 21 short-circuits the semiconductor element 13. That is, in fixing the metallic cap 14 to the board 12, the conductive resin bonding agent 21 ejected from a syringe is applied along the ground electrode 19, the metallic cap 14 overlaps the board 12 such that the conductive resin bonding agent 21 is sandwiched between the ground electrode 19 and the outer-peripheral-portion lower surface of the metallic cap 14, and the metallic cap 14 is held down. Therefore, when the metallic cap 14 is held down on the ground electrode 19, the conductive resin bonding agent 21 is pushed out from between the ground electrode 19 and the metallic cap 14, and the conductive resin bonding agent 21 flowing out to the inside possibly comes into contact with a signal input/output pad 16 or a power feeding pad 16. Because the conductive resin bonding agent 21 is in contact with the ground electrode 19 to become a ground potential, unfortunately the conductive resin bonding agent 21 makes a short circuit when coming into contact with the pad 16.
Thus, conventionally sufficient flexibility may be put into a distance between the ground electrode 19 and a region where the semiconductor element 13 or the pad 16 is provided. However, when the distance is increased, eventually a footprint of the electronic component 11 is increased to enlarge a size of the electronic component 11. On the other hand, when the size of the electronic component 11 is decreased, the short circuit is easily made by the conductive resin bonding agent 21. Therefore, there is a trade-off relationship between the miniaturization of the electronic component 11 and the prevention of the short circuit.
In the electronic component 11 having the structure of Patent Document 1, a variation in height of the electronic component 11 is generated by a variation in thickness of the conductive resin bonding agent 21. The metallic cap 14 cannot sufficiently be pressed in bonding the metallic cap 14 because possibly the conductive resin bonding agent 21 flows out to the inside to generate the short circuit when the metallic cap 14 is strongly held down in bonding the metallic cap 14 to the conductive resin bonding agent 21. Therefore, the variation in height of the conductive resin bonding agent 21 is generated. Because the height of the electronic component 11 depends on a total of the thickness of the board 12, the height of the metallic cap 14, and the thickness of the conductive resin bonding agent 21, the height of the electronic component 11 varies when the thickness of the conductive resin bonding agent 21 varies. The large thickness of the conductive resin bonding agent 21 prevents a low-height profile of the electronic component 11. The excessively small thickness of the conductive resin bonding agent 21 may result in degrading of bonding strength by a lack of resin amount or generation of a bubble.
FIG. 3 is a sectional view illustrating an electronic component 31 disclosed in Patent Document 2. In the electronic component 31, a high-frequency semiconductor element 34 is mounted on an island portion 33 provided in an upper surface of the board 32, and the island portion 33 is connected to a lead electrode 36 in a rear surface through a via hole 35. An electrode of the semiconductor element 34 is connected to a pad 38 on the board 32 through a bonding wire 37, and the pad 38 is connected to a lead electrode 40 in the rear surface through a via hole 39. A groove portion 41 is provided in the outer peripheral portion in the upper surface of the board 32 by cutting with a dicing blade, and a resin reservoir 43 is formed between the groove portion 41 and the resin cap 42 when the resin cap 42 overlaps the groove portion 41. Therefore, when the lower surface of the resin cap 42 and the groove portion 41 are bonded by a bonding resin 44, the excess bonding resin 44 is retained by the resin reservoir 43, thereby preventing the bonding resin 44 from flowing out onto the side of the semiconductor element 34.
However, in the electronic component 31 having the above-described structure, it is necessary that the board 32 be mechanically cut with the dicing blade to prepare the groove portion 41, which results in cost increase. Because the groove portion 41 is provided after the board 32 is prepared, it is difficult to provide a conductive pattern in the groove portion 41 that is of the bonding portion. Therefore, the electronic component 31 is not suitable to the joining associated with electric conduction between the metallic cap and the conductive pattern (ground electrode) of the board. Further, unfortunately the variation in height of the electronic component 31 is increased by a variation in mechanical cutting of the groove portion 41.
Patent Document 1: Japanese Unexamined Patent Publication No. 2002-134639
Patent Document 2: Japanese Unexamined Patent Publication No. 2002-110833